1. Field of the Invention
The present invention concerns a method of producing multilayered printed-circuit boards and a producing apparatus thereof, and more particularly a method of producing multilayered printed-circuit boards appropriate for preparing a multilayered printed-circuit board appropriate for a package containing semiconductor devices provided with wiring layers comprising mainly of low resistance metals such as copper or through hole conductors filled with metal paste or others material on a surface of an insulating layer containing organic resins and an apparatus for producing same.
2. Background of the Related Art
Conventionally, a method for producing multilayered printed-circuit boards, a technique is utilized comprising the steps of laminating an inner layer material (core material) where a circuit is formed on an dielectric cover and an outer layer material (or conductive foil) through a prepreg, and adhering the inner layer material and the outer layer material by pressurizing and heating them to multilayer.
More in detail, the method comprised the following steps:                1. Perforation of a reference hole in the inner layer material        2. Circuit formation by etching (photolitho process) a copper foil of the inner layer        3. Black oxide treatment of the copper        
The black oxide treatment is performed for the purpose of improvement of resin wetting by forming carpet-shaped pile through oxidation of the copper foil surface for increasing the adhesion resistance between the copper foil and the prepreg, and more specifically, it is performed by the following steps.
Degreasing is followed by soft etching (e.g., chemically roughing the circuit surface of the core material to prepare the board for black oxide treatment) then followed by sulfuric acid washing (having the purpose of removing debris generated by soft etching and rinse) then predep. (a common chemical treatment for preventing liquid from dragging in the black oxide treatment tank) then black oxide treatment then drying (to remove moisture of black oxide treatment).                4. Laminating press        5. Through hole perforation        6. Through hole inner wall covering        7. Circuit formation by etching of copper foil of outer layer (photolitho process)        8. Shape processing        
The laminating press process consists in setting and adhering a non-set resin of the prepreg through pressurizing and heating of blacking treated core material, prepreg and outer layer material (or copper foil).
Conventionally, in the case of using epoxy resin as prepreg, the laminating press process has been carried out under a pressure of 20 to 40 kg/cm2, temperature equal or superior to 170° C. for 20 minutes or longer.
However, in the conventional producing method mentioned above, there was an inconveniency that the resin flowed in quantity after setting, the board thickness was irregular, and the workability was impeded.
On the other hand, recently, black oxide treatment is required also for the high-integration of the multilayered printed-circuit board. As a technology to cope with such requirement, a so-called blind hole technology is being developed. This consists in perforating a through hole beforehand (before press lamination) in the insulator board of the inner layer, covering the through hole with copper, or filling the through hole with conductive paste (thermosetting resin mixed with conductive powder) to obtain a through hole conductor. Such technology is a technology allowing to realize a high black oxide treatment of multilayered printed-circuit board.
However, in the case of applying the aforementioned conventional producing method of multilayered printed-circuit board to such blind hole technology, there was a problem of inhibiting to cope with the filing because of dislocation between a plurality of layers.
The present invention resolves problems of the aforementioned conventional technology, and has an object to provide a method of producing multilayered printed-circuit board that has eliminated the resin flow and resolved the problems of board thickness discrepancy and misregistration.
Thereby, it has an object of providing a method of producing highly multilayered and highly precise multilayered printed-circuit boards and producing apparatus maintaining a good productivity and a high reliability.
The present invention has an object to provide an apparatus of producing multilayered printed-circuit board that has limited the board thickness dispersions, improved the workability and eliminated misregistration.